The present invention relates to an exhaust gas cleaning device of an outboard motor unit.
Recently, in order to prevent air contamination and water contamination, a catalyst is disposed in an exhaust passage of an outboard motor unit. Attention is paid to the location of the catalyst because the catalyst is degraded or damaged if in contact with a water component such as sea water.
In one example of a conventional outboard motor unit considering the above problem, an exhaust expansion chamber is disposed below an engine, a first exhaust passage opened to the expansion chamber is disposed, a second exhaust passage is also disposed so as to communicate the expansion chamber with an underwater exhaust port, and a counterflow preventing section is provided on the way of the second exhaust passage. The counterflow preventing section is positioned above a body of a hull to which the outboard motor unit is mounted.
However, in the conventional structure mentioned above, because the counterflow preventing section is formed by bending the exhaust passage, an exhaust resistance is increased, resulting in the lowering of an output power of the engine.